The present invention relates in general to tamper-evident structures for container closures and caps. More specifically, the present invention relates to a container closure assembly that includes a snap-on overcap. The overcap includes a tamper-evident feature. The specific style of container closure for use with the disclosed snap-on overcap, as described for the present invention, includes a bung style plug that threads into an internally-threaded container opening. In one embodiment of the present invention, the bung style plug includes a central portion arranged with internal, modified buttress threads and the overcap includes a centrally-positioned post that is constructed and arranged with a series of cooperating external, modified buttress threads. These external threads are designed to engage and interlock with the internal threads of the bung style plug for an axially-directed snap fit of the overcap into and over the bung style plug. The requisite flexing of the external threads for this snap-on assembly with the plug is enabled by the modified buttress thread form and the plastic construction.
One of the improvements provided by the present invention is the ability to provide a tamper-evident structure in combination with a bung style plug. Another improvement provided by the present invention is found in the simplicity of the overcap and the ease of assembly into and over the bung style plug.